Genealogies from the Mexican-American city of Laredo, Texas are compiled from civil and church birth, death, and marriage records. The city will thus be ascertained more or less totally and without any bias relative to biomedical studies. Cause of death will be mapped onto these genealogies. The genalogies will be examined stastically to determine whether, and to what extent, there is familial clustering of death due to cancer in general or cancer at varius organ sites. Demographic data, including fertility, will be applied both to the assembly, by computer, of genealogies and to the analysis of the cause of death patterns. By parameterizing death rates by age, we hope to express this risk in terms which are meaningfully related to underlying biological processes related to human aging and to the causation of cancer itself. Competing causes of death will be taken into account in our analysis, which will also test for first-order environmental effects by examining the genalogies for cancer clustering when unrelated individuals (i.e. spouses) have been substituted into them. Our genealogies reach back to the 18th century, with cause of death information beginning about 1900.